It has become increasingly common for machines used in agricultural, construction and mining operations to be powered by alternative fuels. The use of liquid natural gas (LNG) for powering movable machines is becoming increasingly popular. Among other things, LNG engines have a reduced carbon output and thus are viewed as more environmentally friendly than conventional diesel and other internal combustion engines powered by gasoline. In addition, given the prevalence of LNG, the cost associated with such fuel is typically lower than other fuel products, and, thus, consumer demand for such machines is increasing.
In order to provide the natural gas to the engine in a portable, efficient manner, the natural gas is cooled to a liquid state and stored on board the machine in a cryogenic tank (cryo-tank). Such tanks are typically double-walled with insulation between the walls in order to maintain the natural gas at a cold temperature and under pressure (such as, at −160° C. and lower, and at pressures at least as high as 300 psi, for example). A pump is then used to deliver the LNG to the engine of the machine. Such pumps, also referred to as a cryogenic pump, are typically provided as piston pumps, which not only deliver the LNG to the engine but also pressurize the LNG to convert it to compressed natural gas (CNG). For example, LNG is typically stored at a pressure of about 300 psi, and CNG is typically at least an order of magnitude greater, such as, about 6000 psi, for example.
U.S. Patent Application Publication No. US2007/0031271 is entitled, “Effervescent Gas Bleeder Apparatus,” and is directed to a diaphragm metering pump suitable for metering an effervescent gas. The pump has a pump head with a product chamber having an inlet end with a one-way inlet valve and an outlet end with a one-way outlet valve. A displaceable diaphragm member defines a boundary of the product chamber. The diaphragm member is capable of being reciprocated to cause pumping displacements. A discharge side is disposed downstream from the outlet valve. A passageway is disposed in fluid communication between the discharge side and the product chamber. A valve is disposed in the passageway. The valve is opened intermittently to allow liquid to re-enter the product chamber in an amount effective to purge gas from the product chamber to prevent loss of prime.
There is a continued need in the art to provide additional solutions to enhance the performance of components of a cryogenic pump system. For example, a cryogenic pump system used on a mobile application preferably meets stringent life and performance requirements to satisfy customer expectations. Furthermore, in mobile applications, the available options for powering the cryogenic pump system are limited, and the cryogenic pump system is just one of many subsystems of a mobile machine vying for a limited power supply. As such, there is a continued need to provide a cryogenic pump system which uses robust control components that can withstand the rigors of the environment within which mobile machines can be used, yet have reduced power demands.
It will be appreciated that this background description has been created by the inventors to aid the reader, and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some respects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any disclosed feature to solve any specific problem noted herein.